A 3-Year Statistical Analysis of Warm Season Convective Rain Diurnal Cycle over SGP and Ngp Based on Precipitation Intensity Classification

Warm season (April to September) convective rain (CR) features more intense rainfall rates compared to longer-lasting, larger-coverage stratiform rain (SR), and usually associate with nocturnal precipitation maximum over the Great Plains. In order to investigate whether this diurnal pattern could hold over the different regions and different CR intensity, the Southern Great Plains (SGP) and Northern Great Plains (NGP) are selected as study regions for their marginal locations within mid-latitude (30^o N to 60^o N), and the convective rain events over each region are objectively classified in to heavy, moderate, and light cases according to the corresponding CR intensity distribution. Despite the difference in climatology, for both regions, moderate and light cases share a common elevated convective core feature (~ 3 km) from the Contoured-Frequency-with-Altitude Diagrams (CFADs) generated using all CR radar columns over the corresponding study domain, while the heavy cases with nocturnal precipitation maximum all have the convective core attach to the surface. From the perspective of diurnal cycles, both regions’ non-heavy CR demonstrate strong dependence on the Planetary Boundary Layer (PBL) height and instability, especially for SGP, whose non-heavy CR precipitation amount and coverage maxima coincide with local sunrise (0700 local time) when the most stable PBL occurs with the lowest PBL height. Though for both regions the moderate CR with elevated convective core also demonstrate nocturnal peaks with more number of cases than heavy CR (216 vs. 98 for SGP, 181 vs. 96 for NGP), their contribution to the nighttime precipitation maxima is one order of magnitude less than that of heavy CR without the feature of elevated convective core. Thus, speculation has been made that the elevated convections may not be the major reason for the nocturnal maximum precipitation, which is more like to be caused by surface-based convections.